Re: [PATCH v2 2/5] powerpc/pseries: Add RTAS error injection buffer infrastructure

[Narayana Murty N <nnmlinux@linux.ibm.com>]

On 10/06/26 8:57 AM, Sourabh Jain wrote:
>
>
> On 27/05/26 12:54, Narayana Murty N wrote:
>> Adds global infrastructure required by the injection engine:
>>   - a 1KB aligned RTAS working buffer in rtas.c
>>   - a spinlock to serialize buffer access
>>   - UAPI definitions for error-injection tokens (added to eeh.h)
>>
>> Signed-off-by: Narayana Murty N <nnmlinux@linux.ibm.com>
>> ---
>>   arch/powerpc/include/asm/rtas.h     | 21 +++++++++++++++++++++
>>   arch/powerpc/include/uapi/asm/eeh.h | 18 ++++++++++++++++++
>>   arch/powerpc/kernel/rtas.c          | 12 ++++++++++++
>>   3 files changed, 51 insertions(+)
>>
>> diff --git a/arch/powerpc/include/asm/rtas.h 
>> b/arch/powerpc/include/asm/rtas.h
>> index d046bbd5017d..82512f822c7a 100644
>> --- a/arch/powerpc/include/asm/rtas.h
>> +++ b/arch/powerpc/include/asm/rtas.h
>> @@ -519,6 +519,27 @@ int rtas_get_error_log_max(void);
>>   extern spinlock_t rtas_data_buf_lock;
>>   extern char rtas_data_buf[RTAS_DATA_BUF_SIZE];
>>   +/*
>> + * RTAS Error Injection Buffer (PAPR-compliant)
>> + * ============================================
>> + *
>> + * 1KB aligned, zero-initialized buffer for ibm,errinjct RTAS work 
>> area.
>> + * Protected by rtas_errinjct_buf_lock for concurrent access safety.
>> + *
>> + * PAPR Requirement: ibm,errinjct requires a caller-allocated buffer 
>> passed
>> + * via physical address. Buffer must accommodate largest error type 
>> layouts:
>> + * - IOA bus error (64-bit): 8x32-bit words (32 bytes)
>> + * - All other types: <=4x32-bit words (16 bytes)
>> + *
>> + * Usage:
>> + * prepare_errinjct_buffer() -> spin_lock() -> rtas_call() -> 
>> spin_unlock()
>> + *
>> + * Alignment: SZ_1K ensures PAPR firmware requirements and 
>> cache-line safety.
>> + */
>> +#define RTAS_ERRINJCT_BUF_SIZE 1024
>> +extern spinlock_t rtas_errinjct_buf_lock;
>> +extern char rtas_errinjct_buf[RTAS_ERRINJCT_BUF_SIZE];
>
> The kernel has a similar buffer for userspace (named rtas_rmo_buf),
> which is allocated in the range (0, min(ppc64_rma_size, 
> RTAS_INSTANTIATE_MAX)).
>
> Whereas, the base address of the statically allocated 
> rtas_errinjct_buf array
> depends on the location at which the kernel is loaded, which could be 
> higher than
> RTAS_INSTANTIATE_MAX.
>
> Also, things will break if the base address of rtas_errinjct_buf is 
> greater than
> 4 GB. In that case, the kernel will send a truncated address, and RTAS 
> may
> corrupt memory as a result.
>
> Why don't we allocate rtas_errinjct_buf in the same range where
> rtas_rmo_buf is allocated?
Yes, I do agree for the design direction and is addressed in V3 patch
https://lore.kernel.org/all/20260721033815.5300-1-nnmlinux@linux.ibm.com/
>> +
>>   /* RMO buffer reserved for user-space RTAS use */
>>   extern unsigned long rtas_rmo_buf;
>>   diff --git a/arch/powerpc/include/uapi/asm/eeh.h 
>> b/arch/powerpc/include/uapi/asm/eeh.h
>> index 3b5c47ff3fc4..86645cab2827 100644
>> --- a/arch/powerpc/include/uapi/asm/eeh.h
>> +++ b/arch/powerpc/include/uapi/asm/eeh.h
>> @@ -41,4 +41,22 @@
>>   #define EEH_ERR_FUNC_DMA_WR_TARGET    19
>>   #define EEH_ERR_FUNC_MAX        19
>>   +/* RTAS PCI Error Injection Token Types */
>> +#define RTAS_ERR_TYPE_FATAL                     0x1
>> +#define RTAS_ERR_TYPE_RECOVERED_RANDOM_EVENT    0x2
>> +#define RTAS_ERR_TYPE_RECOVERED_SPECIAL_EVENT   0x3
>> +#define RTAS_ERR_TYPE_CORRUPTED_PAGE            0x4
>> +#define RTAS_ERR_TYPE_CORRUPTED_SLB             0x5
>> +#define RTAS_ERR_TYPE_TRANSLATOR_FAILURE        0x6
>> +#define RTAS_ERR_TYPE_IOA_BUS_ERROR             0x7
>> +#define RTAS_ERR_TYPE_PLATFORM_SPECIFIC         0x8
>> +#define RTAS_ERR_TYPE_CORRUPTED_DCACHE_START    0x9
>> +#define RTAS_ERR_TYPE_CORRUPTED_DCACHE_END      0xA
>> +#define RTAS_ERR_TYPE_CORRUPTED_ICACHE_START    0xB
>> +#define RTAS_ERR_TYPE_CORRUPTED_ICACHE_END      0xC
>> +#define RTAS_ERR_TYPE_CORRUPTED_TLB_START       0xD
>> +#define RTAS_ERR_TYPE_CORRUPTED_TLB_END         0xE
>> +#define RTAS_ERR_TYPE_IOA_BUS_ERROR_64          0xF
>> +#define RTAS_ERR_TYPE_UPSTREAM_IO_ERROR         0x10
>> +
>>   #endif /* _ASM_POWERPC_EEH_H */
>> diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
>> index a2dd94eed9d0..c110965ea1d9 100644
>> --- a/arch/powerpc/kernel/rtas.c
>> +++ b/arch/powerpc/kernel/rtas.c
>> @@ -769,6 +769,18 @@ EXPORT_SYMBOL_GPL(rtas_data_buf);
>>     unsigned long rtas_rmo_buf;
>>   +/*
>> + * RTAS Error Injection Buffer - Global Definitions
>> + * Global 1KB buffer and spinlock for ibm,errinjct RTAS service.
>> + * Exported for pseries EEH error injection usage.
>> + */
>> +
>> +DEFINE_SPINLOCK(rtas_errinjct_buf_lock);
>> +EXPORT_SYMBOL_GPL(rtas_errinjct_buf_lock);
>> +
>> +char rtas_errinjct_buf[1024] __aligned(SZ_1K);
>> +EXPORT_SYMBOL_GPL(rtas_errinjct_buf);
>> +
>>   /*
>>    * If non-NULL, this gets called when the kernel terminates.
>>    * This is done like this so rtas_flash can be a module.
>
Thanks,
Narayana